Field
Aspects of the present invention generally relate to a probe that receives an acoustic wave generated from an object, an object information acquisition apparatus, and a method of manufacturing the probe.
Description of the Related Art
One of optical imaging techniques may be a photoacoustic imaging technique called photoacoustic tomography (PAT). The photoacoustic imaging is a technique that detects an acoustic wave (also called “photoacoustic wave”) generated because of irradiation with light, and generates image data from an obtained receive signal. This photoacoustic wave is generated when an object is irradiated with pulsed light from a light source, and a tissue which has absorbed the energy of the light propagating in the object is vibrated. The wavelength of this acoustic wave depends on the size of the tissue, and is typically in a wavelength range of ultrasonic waves.
Japanese Patent Laid-Open No. 2010-075681 suggests a probe including an element that receives such an acoustic wave. In the photoacoustic imaging, if the light for generating the acoustic wave is incident on a receive surface of the element in the probe, an acoustic wave is generated at the receive surface, and the generated acoustic wave may cause noise. To restrict the acoustic wave generated at the receive surface, the probe described in Japanese Patent Laid-Open No. 2010-075681 has a light reflection layer directly on the receive surface of the element in the probe so that the light is not incident on the receive surface.
Also, a capacitive micromachined ultrasonic transducer (CMUT) manufactured by using a micromachining technique is studied as a substitute of a piezoelectric element. CMUT is a transducer including a capacitive element. CMUT can transmit and receive an acoustic wave such as an ultrasonic wave by using vibration of a vibration membrane. CMUT can obtain a good broadband characteristic particularly in liquid.
In the capacitive transducer, an acoustic wave may be generated when irradiation light for generating an acoustic wave is incident on a receive surface of an element, and the acoustic wave may cause noise. However, if the light reflection layer is arranged directly on the element like Japanese Patent Laid-Open No. 2010-075681, a stress of the light reflection layer may cause a change in spring constant of a vibration membrane forming the element, a variation in deformation of the vibration membrane, and the like. The influence on the vibration membrane may cause a decrease and a variation in sensitivity of the element, and a decrease in bandwidth.